High intensity discharge (HID) lamps are used in many applications because of their long life and high efficiency. Principal types of HID lamps are high pressure sodium (HPS), pulse start metal halide (PSMH), and mercury vapor lamps.
Mercury vapor, metal halide, and HPS lamps all operate similarly during stabilized lamp operations. The visible light output results from the ionization of gases confined within an envelope and which must be broken down before there is any flow of ionization current. Accordingly, a high open circuit voltage must be applied to an HID lamp for igniting. This voltage is substantially higher than the operating voltage and the available line voltage.
HID lamps also exhibit negative resistance. When operating, their resistance decreases with increase in the applied voltage. As a result, such lamps require an impedance means in their power supply to limit the alternating current flow to a predetermined value.
Because of the high starting or igniting voltage requirement and the negative resistance characteristic, HID lamps are provided with igniting and operating circuits, which provide a relatively high open circuit voltage and impedance means for current limitations. A ballast between the power supply and lamp typically serves as its impedance means in igniting and operating circuits for HID lamps. For HID lamps such as mercury vapor lamps, igniting voltages can be two times the operating voltage. The igniting voltage is generated by the ballast secondary coil winding. For high pressure sodium (HPS) lamps, the required voltages can be more than ten times the operating voltages and more complex igniting mechanisms are employed.
The ballast system also typically provides for certain requirements when electronic igniters are used in conjunction with the HID lamps. For example, electronic igniters used in conjunction with high pressure sodium (HPS) ballast coils produce a high voltage pulse to start the HPS lamp. These electronic igniters work by sensing whether the lamp is burning or not. If the lamp is not burning, the igniter continuously supplies starting pulses to the lamp, regardless of whether the lamp is not burning because of lamp failure, absence of a lamp in the lamp socket, or by the lamp “cycling off.”
Lamp cycling is a well-known phenomenon in which a lamp nearing the end of its life will light, turn on for some time, go out, relight, and repeat this cycle time after time until the lamp is replaced or the lamp will fail to start at all. In an HPS lamp, as the HPS lamp nears the end of its life, its lamp operating voltage gets so high that the ballast will no longer sustain operation, and the lamp cycling condition manifests itself.
From the foregoing, it is clear that certain problems can arise in the operation of HID lamps and associated ballasts. In certain situations, e.g., when a lamp is cycling, failed or is missing, the igniter in the lamp's HID circuit continues to operate. Such operation shortens igniter and ballast life due to the presence of continuous high voltage pulses that inflict unusual, extended stress on the lighting system. The result of this stress on the ballast transformer may result in burning or smoking, damaged HID lamp fixtures, and wiring. Cycling lamps can be also avoid replacement by being “on” when inspected and thus cause future maintenance problems.
High intensity discharge (HID) lamps are used in roadway lighting, manufacturing installations with high/inaccessible ceilings, military installations, aircraft hangars, parking lots, tennis courts, athletic arenas and the like. Replacement of a failed lamp installation can be time-consuming and require specialized access equipment not always immediately available. Maintenance and operational inspections can be infrequent. Frequently, replacement of the lamp of a failed lamp installation is the first step. If the lamp is not the cause of the lamp outage, the cause can be a failed igniter or failed ballast or both. The cause may not be determined until the failed element is replaced and operating power is applied.
The ability to make an operating/problem diagnosis from the ground without access to the lamp installation overhead is an advantage. To determine the cause of the failed lamp installation to order the requisite replacement components and to schedule the repair in a manner that minimizes disruption to the facility where the HID lamp is located is a further advantage provided by the instant invention in the maintenance and repair of failed HID lamp installations.
In the prior art, U.S. Pat. No. 4,318,031 teaches a visual monitor including a single light indicator for HID lamps not needing a starter and a visual monitor including two light indicators for an HID lamp operating in conjunction with the starter. When the lamp is out, the presence or non-presence of an ignited first light indicator indicates lamp failure or ballast failure, respectively. The blinking or non-blinking of the second light indicator indicates whether or not the starter is producing satisfactory starting pulses. Power source is 60 Hz line voltage.
The visual monitor of U.S. Pat. No. 4,318,031 for an HID lamp and ballast includes a second indicator light circuit connected to the starter having a storage capacitor, a diode connected to said capacitor and conductive at a predetermined voltage and an indicator light connected to said capacitor, wherein when the lamp is not lit, the operating starter producing pulses of short duration of predetermined amplitude causes conduction of said diode and storage on said capacitor. A plurality of pulses causes capacitor discharge through said indicator light to cause periodic blinking thereof, the absence of periodic blinking when the lamp is not lit indicating a starter failure.
The visual monitor of U.S. Pat. No. 4,318,031 for a light fixture includes a lamp and a ballast and a starter, said monitor comprising a first indicator light circuit connected in parallel with the lamp and including a first indicator light and the second indicator light connected to the starter wherein absence of ignition of the first indicator light with absence of the lamp being lit indicates ballast failure.
Accordingly, in the prior art it is known to provide visual indicators connected to an HID lamp's ballast and starter to indicate which of the two components of the HID lamp's circuitry, either the ballast or the starter, has failed when the monitored lamp is extinguished. However, the visual device of the instant invention permits rapid identification of failed, broken or missing HID lamps in virtually all applications using HID (high pressure sodium and metal halide) lamps and ballasts equipped with pulse type igniters. A flashing LED signifies a failed lamp, whereas a non-flashing LED signifies a failed ballast or igniter or both.